This invention relates generally to a semiconductor integrated circuit device, and more particularly to a semiconductor integrated circuit technique which is useful for increasing the density of integration and the reliability of a semiconductor integrated circuit device.
Wiring made of aluminum is connected to the source and drain regions formed on the main surface of a MISFET (Metal Insulator Semiconductor Field Effect Transistor) through contact holes. However, aluminum is easily diffused into the source and drain regions due to heat-treatment which is carried out in the production process of a semiconductor integrated circuit device (hereinafter referred to as an "IC"). Here, a problem is encountered that the source and/or drain region is electrically short-circuited to the semiconductor substrate by aluminum that has been diffused into the source and drain regions.
To prevent the diffusion of aluminum into the source and drain regions, a technique has been proposed which disposes a barrier metal between the aluminum wiring and the source and drain regions (C. Y. TING, "Thin Solid Films", Vol. 96, 1982, p 327). This barrier metal has a two-layered structure consisting of a titanium layer as a lower layer and a titanium nitride layer as an upper layer.
The inventors of the present invention have found it difficult to improve the integration density of IC by use of the barrier metal described above. The barrier metal must be formed to be greater than the contact hole in consideration of the variance of mask registration when forming the barrier metal. Moreover, a margin for the mask registration must be secured between the barrier metal formed on a drain region, for example, and a wiring to be connected to a source region. These make it difficult to improve the integration density of IC.
On the other hand, a technique is known which forms a titanium silicide layer on the upper surface of both the source and drain regions of MISFET in order to reduce their sheet resistance (R. D. Davies, "International Electron Devices Meeting, Technical Digest", p 714, 1982).
However, the inventors of the present invention have found that a titanium silicide layer can not be used as the barrier metal for the aluminum wiring because titanium silicide starts reacting with aluminum at about 450.degree. C. Heat treatment at about 450.degree. C. is conducted for a semiconductor chip after the aluminum wiring is formed, too.